2 cups / 14 oz / 400 g split red lentils, picked over and rinsed well
1 tablespoon turmeric
4 tablespoons unsalted butter
fine grain sea salt
1 large onion / ~ 2 cups, diced
2 teaspoons ground cumin
1 1/2 teaspoons yellow mustard seeds
1 cup chopped cilantro
Juice of three lemons, or to taste
1 large bunch of spinach leaves, chopped

plenty of cooked (warm) brown rice, to serve
plenty of plain Greek yogurt, to serve